CN111063530A

CN111063530A - Magnetic core for current detector and method for manufacturing same

Info

Publication number: CN111063530A
Application number: CN201910982368.5A
Authority: CN
Inventors: 永野爱; 北井敦嘉
Original assignee: SHT Corp Ltd
Current assignee: SHT Corp Ltd
Priority date: 2018-10-16
Filing date: 2019-10-16
Publication date: 2020-04-24
Anticipated expiration: 2039-10-16
Also published as: DE102019127729A1; US20200116760A1; US11397195B2; JP2020064931A; JP6461418B1

Abstract

The present invention relates to a magnetic core for a current detector and a method for manufacturing the same. The invention provides a magnetic core for a current detector and a manufacturing method thereof, wherein a plurality of gaps can be formed in a state of maintaining the matching of magnetic chips. A magnetic core (10) for a current detector is provided with: a pair of core pieces (20, 23) formed by cutting an annular core body (12) at 2 points in the radial direction, the core pieces being arranged such that cut surfaces (21, 24) thereof face each other so as to maintain a 1 st gap (26) and a 2 nd gap (28); and a 1 st part mold (30) and a 2 nd part mold (40) which are formed by partially coating the circumferential surface of the cut surface of the magnetic chip facing each other so as to sandwich the 1 st gap and the 2 nd gap with a resin, wherein the 1 st part mold is connected to the 1 st part mold by a bridge (33) so as to sandwich the gap.

Description

Magnetic core for current detector and method for manufacturing same

Technical Field

The present invention relates to a magnetic core for a current detector and a method for manufacturing the same, and more particularly, to a magnetic core in which a plurality of gaps are formed in a magnetic core main body and a method for manufacturing the same.

Background

There is known a current detector in which a magnetic core is formed by forming a gap in an annular magnetic core body made of a magnetic material, a bus bar is disposed on an inner peripheral side of the magnetic core, and a magnetic detection element is disposed in the gap (see, for example, patent document 1).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2007-88019.

Problems to be solved by the invention

In order to improve magnetic characteristics and to adjust magnetic saturation characteristics, a magnetic core in which a plurality of gaps are formed in a core body has also been proposed. For example, 2 gaps are formed in the core body, one gap is provided with a magnetic detection element, and the other gap serves to stabilize the magnetic saturation characteristics.

When the gap is 1, the core is in a state of holding 1 member having a substantially C-shape even if the annular core main body is cut to form the gap, but when 2 gaps are formed, the core main body becomes 2 core pieces and becomes dispersed.

In particular, when a so-called wound core in which a strip-shaped steel sheet is wound is used as a core body, a deviation occurs between the winding start and winding end positions of the steel sheet in the core body. In particular, in the case of a wound core, when the winding strength of the steel sheet is different, the sectional area of the core main body may be different even if the number of windings is the same. In the wound core, although annealing is performed after winding a steel sheet, there are residual stresses in the steps of winding, annealing, dipping in varnish, and the like, and when the core body is cut, the core pieces may be pulled apart by the restoring force of the wound strip-shaped steel sheet. As such, there is a possibility that: when a core is manufactured by dividing core pieces having different cross-sectional areas or by dividing the core pieces, a relative area between the core pieces in the gap is deviated, resulting in a decrease in magnetic permeability, failing to obtain desired magnetic characteristics or magnetic saturation characteristics, and affecting an error rate of linearity or an error rate indicating an error from an ideal B-H in a linear region as an index thereof. When the gap is not formed at the center of the core body, the core pieces obtained by cutting through the gap are asymmetric in the left-right direction. Therefore, it is important to correctly combine the pairs of 2 magnetic chips.

Therefore, it is required to avoid pairing with core pieces manufactured from other core bodies before and after cutting and to use the core pieces cut from the same core body in combination with each other. However, while the core body is cut to manufacture the magnetic chips and the magnetic chips are incorporated into the current detector, it is difficult and complicated to maintain the magnetic chips cut from the same core body in a mated state.

Disclosure of Invention

The invention aims to provide a magnetic core for a current detector and a manufacturing method thereof, wherein a plurality of gaps can be formed in a state of maintaining the matching of magnetic chips.

Means for solving the problems

The magnetic core for a current detector of the present invention includes:

a pair of core pieces formed by cutting an annular core body at 2 in the radial direction, the core pieces being arranged such that cut surfaces thereof face each other so as to maintain a 1 st gap and a 2 nd gap; and

a 1 st part mold and a 2 nd part mold which are obtained by partially coating the circumferential surface of the cut surface of the core piece facing each other so as to sandwich the 1 st gap and the 2 nd gap with a resin,

the part 1 mold includes: a 1 st-1 st mold member for covering one peripheral surface of the cut surface of the core piece facing each other with the 1 st gap interposed therebetween, and a 1 st-2 nd mold member for covering a peripheral surface of the cut surface of the other core piece,

the part 2 mold includes: a 2-1 st mold member for covering one peripheral surface of the cut surface of the core piece facing each other with the 2 nd gap interposed therebetween, and a 2-2 nd mold member for covering a peripheral surface of the cut surface of the other core piece,

at least one of the 1 st-1 st mold member and the 1 st-2 nd mold member or the 2 nd-1 st mold member and the 2 nd-2 nd mold member is connected by a bridge portion formed of the resin.

Preferably, in the part 1 mold, the 1 st-1 st mold member and the 1 st-2 nd mold member are joined by the bridge,

the 2 nd part mold is a structure in which the 2 nd-1 st mold member and the 2 nd-2 nd mold member are not joined,

the bridge portion of the part 1 mold has a groove, and can be bent and cut in the groove.

The bridge portion may be formed on the inner diameter side.

With regard to the current detector of the present invention,

the magnetic detection element is disposed in one or two gaps of the magnetic core for the current detector, and a bus bar is inserted into the center of the magnetic core main body.

The method for manufacturing a magnetic core for a current detector of the present invention includes:

preparing a ring-shaped core body;

a partial mold forming step of partially coating the magnetic core main body with a resin to form a 1 st partial mold and a 2 nd partial mold;

a 1 st gap forming step of forming a 1 st gap by cutting the 1 st part mold and the magnetic core main body in a radial direction at a position where the 1 st part mold is formed; and

a 2 nd gap forming step of cutting the 2 nd part mold and the magnetic core main body in a radial direction at a position where the 2 nd part mold is formed to form a 2 nd gap,

the 1 st gap forming step and/or the 2 nd gap forming step are performed by cutting away a part of the 1 st part mold and/or the 2 nd part mold without cutting off a bridge part connected by the resin.

Effects of the invention

According to the magnetic core for the current detector of the present invention, in the magnetic core, the core pieces are connected to each other by the 1 st portion mold and the 2 nd portion mold after the core pieces are partially covered with the resin when the core main body is cut to form the 1 st gap and the 2 nd gap. At least one of the part 1 mold and the part 2 mold is connected by a bridge portion, so that even if the 1 st gap and the 2 nd gap are formed, the magnetic chips are mated with each other without breaking the bridge portion. Therefore, by incorporating the magnetic core into the current detector in this state, the pairing of the magnetic chips formed of the same magnetic core main body can be maintained. Therefore, even if the core is a wound core formed by winding a steel strip, it is possible to avoid pairing with core pieces of other core bodies before and after cutting the 1 st and 2 nd gaps, and it is possible to use the core pieces cut from the same core body in combination with each other. Therefore, the area of the cut surface facing each other via the gap and the pulling-out due to the restoring force of the steel strip are almost the same, and the magnetic permeability can be prevented from being lowered, so that stable magnetic characteristics or magnetic saturation characteristics can be obtained, and desired linearity or error rate can be obtained. Even in the case of a magnetic core main body in which a gap is formed at an asymmetric position, the mating can be ensured.

Further, the magnetic core for a current detector according to the present invention can maintain the gap interval by the bridge portion connecting the 1 st gap and/or the 2 nd gap, and therefore, when incorporated into a current detector, adjustment of the gap and the like are not necessary. Since the core body is not entirely resin-molded but partially molded, stress acting from the mold to the core due to linear expansion during resin molding such as insert molding or during use can be reduced, and magnetic characteristics can be stabilized.

As for the plurality of gaps formed in the magnetic core, 1 gap is provided with a magnetic detection element, and the other gap can be used for preventing magnetic saturation. In addition, the high-current and low-current magnetic detection elements may be disposed in the 1 st gap and the 2 nd gap, respectively, to detect the high current and the low current. In addition, the same or equivalent magnetic detection elements may be arranged in the 1 st gap and the 2 nd gap to provide redundancy in preparation for a failure of the magnetic detection elements.

According to the method of manufacturing the magnetic core for the current detector of the present invention, in the magnetic core main body, the 1 st and 2 nd part molds are performed in advance at the positions where the 1 st and 2 nd gaps are formed, and the 1 st and 2 nd gaps are formed in the areas after the part molds. In the part 1 mold and/or the part 2 mold, a part of the magnetic core pieces is cut and left as a bridge portion without being cut in the gap forming step, so that the magnetic core pieces are not scattered by the gap forming. Therefore, as described above, the pair of magnetic chips can maintain the gap interval without breaking.

Drawings

Fig. 1 is a plan view of a magnetic core (core) according to an embodiment of the present invention.

Fig. 2 is a plan view of a magnetic core body in which a partial mold is formed.

Fig. 3 is a plan view of a magnetic core of various embodiments of the present invention.

Fig. 4 is a modification of fig. 3.

Fig. 5 is an explanatory view showing an example in which a groove is formed in a bridge portion and the magnetic chips can be bent and cut.

Detailed Description

Hereinafter, a magnetic core 10 according to an embodiment of the present invention will be described with reference to the drawings.

Fig. 1 is a plan view of a magnetic core 10 in one embodiment of the present invention. The core 10 has core pieces (core pieces) 20 and 23 obtained by cutting 2 of the annular core body 12, and the

core pieces

20 and 23 are configured such that cut surfaces 21 and 24 thereof are arranged to face each other so as to form a 1 st gap (gap) 26 and a 2 nd gap 28. The

magnetic chips

20 and 23 are formed with

partial molds

30 and 40 in which the circumferential surfaces (outer circumferential surfaces) of the cut surfaces 21 and 24 facing each other so as to hold the

gaps

26 and 28 are partially covered with resin. Hereinafter, the 2-part mold is appropriately referred to as a 1 st part mold 30 and a 2 nd part mold 40. In the illustrated embodiment, the

gaps

26 and 28 are 2, but if there are a plurality of gaps, the number may be 3 or more.

In the

partial molds

30 and 40, portions to be

bridge portions

33 and 43 described below are preferably formed thicker than other portions as shown in fig. 1. This makes it possible to reliably cut the remaining

bridge portions

33 and 43 even when the

gaps

26 and 28 are cut, and to make the

partial molds

30 and 40 thin as a whole.

In the core 10, as shown in fig. 1, at least one of the

partial molds

30 and 40 spanning the

gaps

26 and 28, preferably two of the partial molds are connected by the

bridge portions

33 and 43 so that the

core pieces

20 and 23 divided into a plurality of parts can maintain at least a ring-like form without being dispersed. In the illustrated embodiment, in the part 1 mold 30, the 1 st-1 st mold member 31 formed around the cut surface 21 of one core piece 20 and the 1 st-2 st mold member 32 formed around the cut surface 24 of the other core piece 23 are coupled by the bridge portion 33. In the part 2 mold 40, a 2 nd-1 st mold member 41 formed around the cut surface 21 of one core piece 20 and a 2 nd-2 nd mold member 42 formed around the cut surface 24 of the other core piece 23 are coupled by a bridge portion 43.

The magnetic core 10 of the present invention can be used as a component of a current detector, for example, a current sensor is configured by inserting a magnetic detection element into one or both of the

gaps

26 and 28 and inserting a bus bar (busbar) into an opening penetrating the center. The gap in which the magnetic sensing element is not inserted functions as a gap for preventing magnetic saturation, for example. Although the widths of the

gaps

26 and 28 are the same in the drawing, the gap width for preventing magnetic saturation may be made narrower by using a wider gap width into which the magnetic detection element is inserted.

In the present invention, the

core pieces

20 and 23 are formed by cutting the annular core body 12. The core body 12 may be made of a magnetic material, and examples thereof include a wound core obtained by winding and annealing a thin plate of a magnetic material, a laminated core obtained by laminating annular thin plates of a magnetic material, and a dust core obtained by dust-molding a magnetic material powder. The present invention can maintain the pairing of the

core pieces

20 and 23 without modification when the core body 12 is cut, and therefore, is particularly preferable for a core formed of

core pieces

20 and 23 having an asymmetric shape in which the formation positions of the

gaps

26 and 28 are shifted from the center in the core body 12 and the winding core having different winding numbers at the start and end of winding.

The

partial molds

30 and 40 are made of an electrically insulating resin, and can be formed by insert molding (insert molding) or the like of the core body 12. Examples of the resin include PPS (polyphenylene sulfide resin), PBT (polybutylene terephthalate resin), and PET (polyethylene terephthalate resin). The insert molding can be performed by, for example, disposing the core body 12 using a metal mold having recesses corresponding to the core body 12 and the

partial molds

30 and 40 and stuffing and seeding a resin in a molten state using various injection molding machines. The

partial molds

30, 40 are provided to partially coat a part of the magnetic core main body 12, that is, the outer periphery of the magnetic core main body 12. When the mold is formed on the entire core body 12, stress is applied to the core body 12 at the time of insert molding, and stress is generated in the core body 12 due to a difference in linear expansion coefficient between the material of the core body 12 and the resin of the mold after the insert molding, so that there is a possibility that the magnetic characteristics of the core body 12 become unstable. On the other hand, by partially molding the

cores

30 and 40, the occurrence of these stresses can be reduced, and the magnetic characteristics of the core body 12 can be stabilized.

In the magnetic core 10 of the present invention, as shown in fig. 2,

partial molds

30 and 40 are formed in the above-described manner at positions where the

gaps

26 and 28 are formed in the annular magnetic core body 12 (partial mold forming step). In the illustrated embodiment, the core body 12 is a rectangular ring-shaped body, but may be circular, oval, or the like. The

partial molds

30 and 40 are formed on the opposite sides of the core body 12, but may be formed on adjacent sides or the same side. When the forming positions of the

gaps

26 and 28 are deviated from the center of the core body 12, the

partial molds

30 and 40 may be formed at the corresponding positions.

Then,

gaps

26, 28 are formed in the core body 12 at positions where the

partial molds

30, 40 are formed by a dicing blade (dicingblade) or the like. The

gaps

26 and 28 are formed until the core body 12 is completely cut in the radial direction and the core body 12 is divided into 2 core pieces 20 and 23 (the 1 st gap forming step and the 2 nd gap forming step). At this time, the

partial molds

30 and 40 are not completely cut as shown in fig. 1, and a part of the

partial molds

30 and 40 is cut so that the 1 st-1 st mold member 31 and the 1 st-2 nd mold member 32 cut so as to sandwich the 1 st gap 26 are connected by the bridge portion 33 and the 2 nd-1 st mold member 41 and the 2 nd-2 nd mold member 42 cut so as to sandwich the 2 nd gap 28 are connected by the bridge portion 43. For example, when the

gaps

26 and 28 are formed by pushing a dicing blade in the radial direction of the core body 12 as shown by the arrow a in fig. 1, the

bridge portions

33 and 43 can be cut so as to remain on the inner diameter side. When cutting is performed from the side surface side, the remaining

bridge parts

33 and 43 are cut on the other side surface side. The remaining thickness of the

bridge parts

33 and 43 needs to be considered depending on the kind of resin, but in the case of PPS, for example, it is preferable to secure 1mm or more. Further, the widths of the

gaps

26, 28 can be appropriately adjusted by changing the thickness of the cutting blade.

In a specific embodiment, when the diameter of the cutting blade used for cutting the magnetic core body 12 and the

partial molds

30 and 40 is about 10cm to 22.5cm, wet cutting can be performed with the rotational speed of the mill set at about 2000 rpm. In order to completely cut the core main body 12 and cut the remaining

bridge portions

33 and 43, it is preferable to use an automatic table-moving type cutting machine which performs control to constantly keep the height of the core main body 12 and the height of the grinder constant.

As described above, by forming the

gaps

26 and 28 in the portions where the

partial molds

30 and 40 are formed in advance, even when the magnetic core main body 12 is cut with a dicing blade, it is possible to make it difficult for chips of the magnetic core main body 12 to remain on the cut surfaces 21 and 24. In particular, when the core body 12 is a wound core, by forming the

partial molds

30 and 40 first, it is possible to prevent metal burrs or barbs that are conductive foreign matter that is averse in the electronic component from being generated in the cut surfaces 21 and 24 when the

gaps

26 and 28 are formed.

As shown in fig. 1, in the magnetic core 10 in which the

gaps

26 and 28 are formed, the

gaps

26 and 28 are formed between the cut surfaces 21 and 24 in the

magnetic core pieces

20 and 23, and the

magnetic core pieces

20 and 23 are maintained in a coupled state by the part 1 mold 30 and the part 2 mold 40 connected by the

bridge portions

33 and 43. Therefore, although the core body 12 is divided into 2

core pieces

20 and 23 in the process of cutting the core body 12 to form the

gaps

26 and 28, the

core pieces

20 and 23 are not dispersed by the

partial molds

30 and 40 and can maintain the ring-shaped form, and therefore, the pair of the

core pieces

20 and 23 formed from the same core body 12 is not broken. Further, since the

magnetic chips

20 and 23 maintain the gap between the

gaps

26 and 28 to be constant by the

bridge portions

33 and 43, adjustment of the gap width and the like are not required.

With respect to the resulting magnetic core 10, a bus bar can be inserted at the center and a magnetic detection element can be disposed in one

gap

26 or 28 to serve as a current detector. A gap in which no magnetic detection element is disposed can be used to adjust the magnetic saturation. Of course, the magnetic detection element may be disposed in the two

gaps

26 and 28. In this case, one is used as the magnetic detection element for high current and the other is used as the magnetic detection element for low current, whereby there are advantages as follows: instead of an expensive magnetic detection element capable of performing magnetic detection in a wide range from a low current to a high current, an inexpensive magnetic detection element having a relatively narrow detection range can be used. In addition, the same or equivalent magnetic detection elements may be used in the

gaps

26 and 28. Thereby, the magnetic detection element is switched when a failure occurs. In other words, the current detector can be made redundant. Further, by averaging the outputs from the two magnetic detection elements, the detection accuracy can also be improved.

Further, since the resin lines of the

partial molds

30 and 40 expand at the use temperature (for example, -40 ℃ to 130 ℃) of the magnetic core 10, the gap between the

gaps

26 and 28 may vary in width. In such a case, it is preferable to use a resin having a linear expansion coefficient close to that of the material of the magnetic core main body 12 for the

partial molding

30, 40. For example, the linear expansion coefficient of the core body 12 is about 1.17 to 1.2X 10^-5In the case of a silicon steel sheet of/° C, the linear expansion coefficient can be about 1.7 to 2.5 × 10^-5PPS at/° C was used as a resin for

partial molding

30, 40.

According to the magnetic core 10 of the present invention, the

partial molds

30 and 40 are formed at the positions where the

gaps

26 and 28 are formed in advance when the plurality of

gaps

26 and 28 are formed, and the

partial molds

30 and 40 are not completely cut and the

bridge parts

33 and 43 are cut when the

gaps

26 and 28 are formed, whereby the

magnetic chips

20 and 23 are not separated from each other. Therefore, the magnetic core 10 of the present invention is particularly preferable for a wound core, and by applying the present invention to a wound core, the areas of the cut surfaces 21, 24 of the

magnetic core pieces

20, 23 according to the number of turns of the electromagnetic steel sheet or the strength of the turns can be made substantially the same, and further, if the

magnetic core pieces

20, 23 are cut from the same core body 12, even if there is residual stress in the steps of winding, annealing, dipping (varnish impregnation) or the like of the magnetic core, the pulling-apart of the

magnetic core pieces

20, 23 after cutting due to the restoring force thereof is made substantially the same, and therefore, when the

magnetic core pieces

20, 23 are faced to each other via the

gaps

26, 28, the cut surfaces 21, 24 are preferably opposed to each other. Therefore, it is possible to suppress a decrease in magnetic permeability due to the variation or deviation in the area of the cut surface, suppress a variation in magnetic characteristics or magnetic saturation characteristics, and suppress an influence on linearity or error rate. The

bridge portions

33 and 43 also have an insulating effect between the bus bars and the core body 12. Further, since the

magnetic chips

20 and 23 having the asymmetrical shapes due to the formation positions of the

gaps

26 and 28 can be maintained as a pair, mounting errors and the like can be reduced.

In the above embodiment, the

gaps

26 and 28 are formed by cutting the

excess bridge parts

33 and 43 in both the

partial molds

30 and 40, but as shown in fig. 3, the gap 26 may be formed by cutting the excess bridge part 33 in one partial mold 30, and the gap 28 may be formed by completely cutting the other partial mold 40 without cutting the excess bridge part. In this case, the partial mold 40 is separated, but the separation position is only 1, and therefore the

magnetic chips

20 and 23 are connected to each other by the bridge portion 33 without being dispersed, and thus the pairing of the

magnetic chips

20 and 23 can be maintained. In this case, as shown in fig. 4, the cutting with the dicing blade can be performed in the direction of arrow B, and the bridge portion 33 can be formed on the outer diameter side in the partial mold 30 to be cut later.

In the case where the gap 26 is formed by leaving the bridge portion 33 only in the one partial mold portion 30 described in fig. 4 and the other partial mold 40 is completely cut, as shown in fig. 5 (a), the bridge portion 33 may be formed with the groove 34 in the width direction. When the slot 34 is incorporated into the current detector, as shown in fig. 5 b, a force (arrow C in fig. 5 b) is applied 1 or more times to the bridge 33 in a direction to reduce the width of the slot 34 so as to grasp the

magnetic chips

20 and 23, whereby the bridge 33 can be bent in the slot 34 to cut the 1 st-1 st mold member 31 and the 1 st-2 nd mold member 32 as shown in fig. 5C. This makes it possible to disperse the

magnetic chips

20 and 23 and to incorporate them with the width of the

gaps

26 and 28 corresponding to the requirements of the current detector. Instead of the groove 34, the bridge portion 33 may be formed thin so as to be easily cut by bending.

The above description is illustrative of the present invention and should not be construed to limit the invention or the scope of the narrowing as set forth in the claims. The configurations of the respective portions of the present invention are not limited to the above-described embodiments, and various modifications can be made within the technical scope described in the claims.

For example, although the widths of the

gaps

26 and 28 are the same in the above embodiment, these widths may be different. The

partial molds

30 and 40 may be provided at least at the positions where the

gaps

26 and 28 are formed, and a partial mold for positioning may be additionally provided in a housing of the current detector or the like.

Description of reference numerals

10 magnetic core

12 magnetic core main body

20 magnetic chip

23 magnetic chip

26 No. 1 gap

28 nd gap 2

30 part 1 casting mould

33 bridge part

40 part 2 casting mould

43 bridge part.

Claims

1. A magnetic core for a current detector, comprising:

2. The magnetic core for a current detector according to claim 1,

in the 1 st part mold, the 1 st-1 st mold member and the 1 st-2 nd mold member are joined by the bridge,

3. The magnetic core for a current detector according to claim 1 or claim 2,

the bridge portion is formed on the inner diameter side.

4. A current detector, wherein a magnetic detection element is disposed in one or both of the gaps of the magnetic core for current detector according to any one of claims 1 to 3, and a bus bar is inserted into the center of the magnetic core main body.

5. A method of manufacturing a magnetic core for a current detector, the method comprising:

preparing a ring-shaped core body;